Vectorization Workflow Diagram

Follow these steps (white blocks are optional) to get started using the Vectorization Advisor in the Intel Advisor.


Vectorization Advisor workflow: Dig Deeper

  • Survey Report - Offers integrated compiler report data and performance data all in one place. Use it to help identify:

    • Where vectorization, or parallelization with threads, will pay off the most

    • If vectorized loops are providing benefit, and if not, why not

    • Un-vectorized loops and why they are not vectorized

    • Performance problems in general

    The Survey Report also provides code-specific recommendations for how to fix vectorization issues, and quick visibility into source code and assembly code.

  • Trip Counts and FLOP analysis - Dynamically identifies the number of times loops are invoked and execute (sometimes called call count/loop count and iteration count respectively); and measures the number of floating-point and integer operations, and memory traffic. Use to make better decisions about your vectorization strategy for particular loops, as well as optimize already-parallel loops.

  • Roofline chart - Helps visualize actual performance against hardware-imposed performance ceilings, as well as determine the main limiting factor (memory bandwidth or compute capacity), thereby providing an ideal roadmap of potential optimization steps.

    Use the Roofline chart to answer the following questions:

    • What is the maximum achievable performance with your current hardware resources?

    • Does your application work optimally on current hardware resources?

    • If not, what are the best candidates for optimization?

    • Is memory bandwidth or compute capacity limiting performance for each optimization candidate?

  • Dependencies Report - For safety purposes, the compiler is often conservative when assuming data dependencies. Use a Dependencies-focused Refinement Report to check for real data dependencies in loops the compiler did not vectorize because of assumed dependencies. If real dependencies are detected, the analysis can provide additional details to help resolve the dependencies. Your objective: Identify and better characterize real data dependencies that could make forced vectorization unsafe.

  • Memory Access Patterns (MAP) Report - Use a MAP-focused Refinement Report to check for various memory issues, such as non-contiguous memory accesses and unit stride vs. non-unit stride accesses. Your objective: Eliminate issues that could lead to significant vector code execution slowdown or block automatic vectorization by the compiler.

For more complete information about compiler optimizations, see our Optimization Notice.